1. Field of the Invention
The present invention relates to a time signal repeater which relays a radio signal including a time code for a radio correction clock receiving a radio signal to correct its time and to a time correction system using the same.
2. Description of the Related Art
A radio correction clock receives, for example, a standard time radio signal of a long wave (for example, 40 kHz in Japan) transmitting a standard time and corrects the time based on the received radio signal to display the precise time.
This type of radio correction clock has built into it a receiving circuit receiving a standard time radio signal and a control circuit for driving a hand driving system based on the received signal to correct the time. In the radio correction clock, the positions of the hands are corrected to positions according to the time code of the received radio signal.
A radio correction clock exclusively receives the standard time radio signal. There are many cases where it is placed in a location which the radio signal can hardly reach, for example, is in an apartment building or basement, and cannot receive the signal.
In order to eliminate this restriction on the location where the radio correction clock is placed, it has been proposed to provide a time signal repeater for receiving the standard time radio signal and modulating the received time signal by a predetermined carrier and transmitting the modulated signal, and to have the radio correction clock receive the signal transmitted from the repeater to correct the time (see for example Japanese Unexamined Patent Publication (Kokai) No. 5-333170).
Summarizing the problem to be solved by the invention, the above time signal repeater transmits the generated time radio signal with a predetermined field intensity.
When a time signal repeater transmits a time radio signal with a field intensity enabling a radio correction clock set a long distance from the time signal repeater to receive it normally, however, the field intensity of the transmitted time radio signal will be too strong at a radio correction clock set comparatively close to the time signal repeater. As a result, so-called "input saturation" will occur and the radio correction clock may no longer be able to normally receive the time radio signal from the time signal repeater.
In this case, it is necessary to turn a radio correction clock set comparatively close to the time signal repeater in a direction with poor directivity, so complicated trouble is necessary.